Climate Science

Early Reversals

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Science  22 Jun 2007:
Vol. 316, Issue 5832, pp. 1670
DOI: 10.1126/science.316.5832.1670d

Over the Pleistocene epoch, sea level was more than 100 m lower during some glacial periods than it is now; even within cold intervals, it may have varied by tens of meters. During the last interglacial, global average temperatures were near where they are expected to be in the coming century, and sea level was 4 to 6 m higher. Thus, conditions in that period seem relevant to our near future. Recently compiled evidence suggests that sea levels fluctuated by as much as 30 to 40 m during the beginning of that warm interval, but the large changes inferred have been controversial due to a lack of corroborating records. Andrews et al. have confirmed the variability using deposits that record the relative elevations of the Greek shoreline. By precisely determining the sample ages via U/Th dating, they found that sea level twice dropped precipitously between 136,000 and 135,000 years ago, near the end of deglaciation, an observation that supports earlier findings from the Red Sea and from Papua, New Guinea. Their results also help to constrain the timing of sea-level rise during the penultimate deglaciation. — HJS

Earth Planet. Sci. Lett. 10.1016/j.epsl.2007.05.005 (2007).

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